Originally Posted by tlk
I noticed that when I am trying to use my honady comparator on some brands of brass I am geting over .001 of variance when I spin the cases in the calipers and the comparator, and all of the chatter is coming from the case head on the caliper jaws.
How much variation? How are you measuring variation? Over 0.001" isn't particularely specific. If you measure one case over and over spinning it around writing down every measurement how much variation do you see? Of the measurements taken that show variation which one do you think is the most correct of the set?
The reason I ask is that I'm not convinced that 0.001 or even slightly over 0.001" like 0.002" crush variation matters at all for accuracy. Trying for 0.001" extreme spread repeatability on something as flexable and springy as cartridge brass using a gross measurement tool like a digital caliper is like trying to slice cheese with optical precision for a couple of reasons.
Digital calipers aren't good for 0.001" extreme spread in any absolute statistical sense from day to day. Micrometers are but not digital calipers.
The brass can't be counted on to repeat within .001" extreme spread from case to case.
The reason neck sizing can work at all is because the brass has spring back from even as precise a process as the fireforming that happens in a chamber when the round is fired which is the most repeatable thing one ever does with brass. The good news is that springback makes brass usable because with out it extraction of fired cases would be quite difficult. The bad news is that springback makes rifles cases poor candidates for extreme precision when it comes to shoulder set back.
This is further complicated by the fact that nearly all bolt actions (except maybe Savages with their floating bolt head) have 0.001" or more of change in the plane of the bolt face itself between the time the firing pin hits the primer and the bullet leaves the brass because the bolt flops up and down in the rear (which is why bolts are sleeved on some benchrest rifles and some long range rifles).
I could see gently dragging the base across some 800 grit emery to get rid of a burr on some cases just to make measurement easier though I've never done that. Machining the base in a Wilson trimmer might make one feel better but unless it's done very carefully it could result in thinning the rim and increasing the probability of extraction problems.
If it contributes to the fun of reloading and shooting, or eliminates some frustration, with the measurement process, go for it, but I seriously doubt there is any significant difference between brass that's had either process applied and brass not subjected to either process on either the target or game.